U.S. Pat. No. 4,667,633 (corresponding to German Patent Application No. 33 43 481) describes a method and an apparatus for monitoring a system for controlling an internal combustion engine. There, in the case of a diesel internal combustion engine, during coasting the control rod is activated in such a way that the quantity of fuel to be injected becomes zero. A check is made by means of a so-called needle movement sensor as to whether injections are still occurring. If no injection pulses are occurring, the system is fault-free.
German Patent Application No. 196 20 039 describes a system for controlling a diesel internal combustion engine in which the quantity of air supplied to the internal combustion engine can be controlled by means of a throttle valve. This system further comprises a means for controlling the exhaust gas re-circulation rate, and a device for compressing the air supplied to the internal combustion engine.